The present invention relates to peptides that may be used to prevent nuclear translocation of proteins which naturally associate with Imp7 as a means for translocating into the nucleus. The peptides may be used for the treatment of inflammatory and immune diseases. Further, the peptides may be used to promote nuclear translocation of proteins and other compounds into the cell nucleus when attached thereto.
To ensure accurate cellular functioning, the spatial distribution of proteins needs to be tightly regulated and coordinated. This is particularly apparent in many signaling proteins that dynamically and rapidly change their localization upon extracellular stimulation. In order to maintain such regulation, the nucleus is separated from the cytoplasm by a double membrane envelope that allows for a selective entrance of proteins through specialized nuclear pore complexes (NPC). The selectivity of nuclear localization is primarily mediated by a nuclear localization signal (NLS) harbored within the sequence of the nuclear protein [G. Schlenstedt, FEBS Lett 389, 75 (Jun. 24, 1996)].
The major type of NLS identified thus far is composed of basic amino acids which are required for the mechanism of entrance through the NPC. These basic sequences come in two flavors: (i) a single stretch of five to six basic amino acids, exemplified by the simian virus (SV) 40 large T antigen NLS; and (ii) a bipartite NLS composed of two basic amino acids, a spacer region of 10-12 amino acids, and a cluster in which three of five amino acids must be basic. This type is typified by nucleoplasmin. For NLS-mediated nuclear import to occur, the NLS first associates with the cytosolic import-receptor proteins importin α and β, which allows docking at the cytoplasmic side of the nuclear pore [E. J. Tran, S. R. Wente, Cell 125, 1041 (Jun. 16, 2006)]. Movement through the nuclear pore is regulated by the small GTPase Ran, which in its GTP-bound state promotes the dissociation of the imported protein from the importins and their recycling back to the cytoplasm [J. Moroianu, J Cell Biochem Suppl 32-33, 76 (1999)].
However, not all cyto-nuclear shuttling proteins contain the canonical NLS, and therefore use other, NLS-independent, mechanisms for their passage through the NPC. Some of the characterized NLS-independent mechanisms include passive diffusion of small proteins (<30-40 kDa), distinct nuclear-directing motifs [D. Christophe, C. Christophe-Hobertus, B. Pichon, Cell Signal 12, 337 (May, 2000)], interaction with NLS-containing proteins, or alternatively, a direct interaction with the nuclear pore proteins (NUPs); [L. Xu, J. Massague, Nat Rev Mol Cell Biol 5, 209 (March, 2004)]. However, the kinetics of shuttling and nuclear retention by these mechanisms are usually too slow to allow timely transient transcription, and therefore the molecular mechanism(s) that allows the rapid and reversible NLS-independent translocation of signaling proteins upon stimulation is still obscure.
Chuderland et al, 2008, Mol Cell 31, 850-861 and Plotnikov et al., 2011, Mol Cell Biol 31, 3515-3530 teach that ERK1/2 translocation involves CK2-mediated phosphorylation of two Ser residues within a nuclear translocation signal (NTS) of ERK1/2. This phosphorylation allows interaction with Imp7, which further facilitates ERK1/2 shuttling via nuclear pores.
The ability to regulate the cellular localization of a biological component is important for many functions such as the regulation of nucleic acid expression, transfection of eukaryotic cells, gene therapy, protection from toxic chemicals and transport of anti-cancer agents. There is thus a widely recognized need for, and it would be highly advantageous to identify novel sequences capable of regulating nuclear translocation.
Additional background art includes U.S. Patent Application No. 20100099627.